Once a pipeline of perpetual Grand Slam champions from Bill Tilden and Don Budge to Jimmy Connors and John McEnroe and Pete Sampras and Andre Agassi, the USA has fallen on hard times.

"There is no running around that question," said veteran Robby Ginepri, the only active American man with a Grand Slam semifinal on his résumé (2005 U.S. Open). "The guys haven't been able to keep a higher standard after Pete and Andre left."

Roddick, 30, a former No.1 and mainstay in the top 10 for years, abruptly pulled the plug on his career at last year's U.S. Open. Another recent top-10 player, Mardy Fish, has dealt with a heart ailment plus related and psychological problems that have kept him off the Tour for most of the last 12 months.

Under Patrick McEnroe and top development lieutenant Jose Higueras, the USTA has focused on building regional training centers across the land and emphasizing more play on clay, where the fundamentals of point construction tend to come easier.

In a ESPN conference call with news reporters last week, McEnroe cited several factors for the performance drop, from the globalization of tennis, which means no one country can dominate, to the need for luring better athletes at a young age into the sport.

Andy Roddick won the U.S. Open in 2003, the last time an American man has won a major.(Photo: Todd Plitt, USA TODAY)

Champions don't always emerge from national programs — and often emerge outside of them, such as Venus and Serena Williams.

"Whether we can find those ones that can get to the promised land, nobody has the answer to that," he said. "A lot of times ... great players come out of nowhere or develop on their own. But we're certainly trying to do everything we can to make the overall level of play in the pipeline stronger."

Tim Mayotte sees a deeper cultural problem: a systemic failure to adapt technique and style that has left Americans unable to neutralize and defend, which is now the key to top-level success.

"The model is broken," says Mayotte, a former top-10 player who worked under McEnroe at the USTA but last year opened his own tennis academy a few miles away from the National Tennis Center in Queens.

"They are forced to hit overly aggressive forehands from out of position or weak backhands that get killed," Mayotte says of a problem affecting most of the top American men since the turn of the century, from Roddick and James Blake to Querrey and Isner to lauded youngsters such as Jack Sock and Ryan Harrison.

Mayotte, the 1981 NCAA champion from Stanford, isn't the only one who has noticed this trend.

"The American players over the last sort of, I would say 10 to 15 years, they actually have a pretty set way of playing," defending U.S. Open champion Andy Murray said in a recent conference call. "Most of their guys have big serve, big forehand."

Mayotte, who left the USTA partly because of differing philosophical views with McEnroe and Higueras, thinks instructors have "lost their way. I think we can accelerate the process by learning to neutralize. Our players are not adapting to that."

But it's not all gloom and doom for the Stars and Stripes.

Top-ranked twins Mike and Bob Bryan continue to make doubles history and are aiming to become the second pair to win a calendar year Grand Slam at the U.S. Open, which would be five consecutive major titles.

Isner gave the men a shot in the arm by beating three top-10 players, including No.1 Novak Djokvic, in reaching the final in this month's Cincinnati Masters. The big week, which followed a strong summer, propelled him back into the top 20.

McEnroe hopes young players such as Harrison, 21, and Sock, 20, can develop into elite players and is even more optimistic about a younger group of players who have yet to hit the pros.

He also pointed to the women, where the USA, led by No.1 Serena Williams, has 10 players ranked in the top 100, more than any other country.

"No one wants to see more Americans more than we do," McEnroe said.

For now, he'll have to settle for six men ranked in the top 100, but only one, 28-year-old Isner, in the top 30.

Several leading U.S. players sounded weary of the line of questioning in the Western & Southern Open outside Cincinnati this month. The general feeling: Not my problem.

"We miss Andy, for sure," Fish said of Roddick. "But there's no doubt that some guys need to step up. I did as well as I could for a lot of years being in the sort of top 25-ish, and the last four years being inside the top 15 for the most part. I think you might want to ask them."

Ginepri, 30, says he would never have imagined that when he, Roddick, Blake and Fish were emerging a decade ago that his 2005 U.S. Open semifinal loss to Agassi would hold up as a statistic of excellence.

"It's tough to look back and see that no one has done anything better," he said.